Theropods from the La Bonita site, Bajo de la Carpa Formation (Neuquén Group, Santonian), Río Negro, Argentina: analysis of dental evidence

Abstract

The abundant record of theropods from Bajo de La Carpa Formation (Neuquén Group, Santonian), known from the end of the nineteenth century, come from numerous locations within the Neuquén Basin. During the excavation of the titanosaur Bonitasaura salgadoi at the La Bonita fossiliferous site, northwest of Río Negro province Argentina, were recovered three isolated teeth assignable to non-avian theropod dinosaurs. Previous studies of these dental materials suggested that MPCA-Pv-247 corresponds to an indeterminate tetanure possibly related to Orkoraptor, a taxon of uncertain phylogenetic position at that moment, and MPCA-Pv-249 and 251 as possible abelisauroids. Three methods were carried out, namely, a cladistic analysis performed on a dentition-based data matrix, and a discriminant and cluster analyses performed in a large dataset including measurements of non-avian theropod teeth. The results assign for the first time a confidently phylogenetic position to the described dental material. The analysis shows that MPCA-Pv 247 belongs to Megaraptoridae, whereas MPCA-Pv 249 and 251 were recovered as belonging to Abelisauridae, supporting in a reliable way the previous assignments. The results show the presence of Megaraptoridae at La Bonita and, additionally, they represent an evidence of the first direct association of megaraptorids and abelisaurids at the same locality of the Bajo de La Carpa Formation, according to similar associations from other units of the Neuquén Group.